Finishing tool



8- 2, 1969 H. w. FERCHLAND 3,460,292

FINISHING TOOL Filed on. 19, 1965 I N VEN TOR.

ATTORNEY 3,460,292 FINISHING TOOL Harold W. Ferchland, Birmingham, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 19, 1965, Ser. No. 497,864 Int. Cl. B24b 7/00, 9/00, 55/02 US. C]. 51-34 6 Claims ABSTRACT OF THE DISCLOSURE SPECIFICATIONS This invention relates to a tool for sizing or reaming a hole and, more particularly, it relates to a tool for finishing or honing to size and true geometry a previously made hole.

There are available today many different types of reaming and sizing tools for finishing a previously made hole. Many of these tools do a reasonably accurate job of finishing the hole until the cutting surfaces wear down. At that time the tool is able to wobble Within the hole which may result in a belling effect at the ends of the hole or barreling in the center of the hole length. Hence, the accuracy of currently available such tools decreases during their lifetime, thereby making them very undesirable.

It is, therefore, an object of this invention to provide a hole finishing tool which is capable of maintaining extremely close tolerances in comparison with currently available such tools. This object is accomplished by mounting the cutting surface of the present invention on an expandable sleeve so that it can be expanded to compensate for wear, thereby maintaining desired tolerances throughout the life of the tool.

Other objects, features and advantages of the subject invention will become apparent upon reference to the following detailed description and the drawings illustrating the preferred embodiment thereof, wherein:

FIGURE 1 is a schematic view of an embodiment of the subject invention in conjunction with a pressurized fluid supply system and a driving tool; and

FIGURE 2 is an enlarged view of an embodiment of the subject invention with parts broken away and in section.

In general, the invention comprises an expandable sleeve including an external cutting surface mounted on a cylindrical body such that it is expandable relative to the cylindrical body under the action of an internal pressurizing system.

More particularly, FIGURE 1 shows a finishing tool 10 attached to a driving mechanism 12 which is adapted to receive power through shank 14 to rotate the tool 10 at a desired rate. The tool 10 may be adapted to the driver 12 by any suitable means 16, such as a locking nut or a rotating expandable chuck. The remainder of FIGURE 1 shows a supply system for a pressurized fluid which is used within the finishing tool 10. This system includes a supply tank 18, a pump 20, a pressure relief 3,460,292 Patented Aug. 12, 1969 valve 22, a throttle valve 24, and a pressure gauge 26. The fluid within the tank 18 is pulled by means of the pump 20 through the conduit 28 and fed through the throttle valve 24 into the driver 12. The pressurized fluid is then conducted through the driver :12 into the finishing tool 10. The pressure relief valve 22 is designed to control the pressure of the fluid flowing into the driver 12 by bleeding some of the fluid through the conduit 30 back into the tank 18. The pressure gauge 26 may be of any suitable type serving the purpose of indicating the pressure of the fluid entering the driver 12 so that it can be controlled by means of either the pressure relief valve 22, or the throttle valve 24, or both valves. The type of fluid used within this system and stored in the tank 18 may be of any suitable, incompressible type. However, for purposes to be discussed later, it is desirable that it have good lubrication properties. The function and use of this pressurized fluid will become more readily apparent upon considering the following discussion relating to the structural and operational details of the subject invention as it is embodied in the finishing tool 10 as shown in FIGURE 2.

FIGURE 2. shows a long cylindrical body or core 32 which has a blunt nose or work entering head 34. The cylindrical body or core 32 has an annular relief 42 therein over a portion of its length. An annular expandable sleeve 40 with a very thin section overlies the relief 42 and forms an annular chamber 44 between the body 32 and the sleeve 40. The annular sleeve 40 has a flange 38 including an O-ring seal whereby the flange is adapted to cooperate with the tool receiving means 16 to secure the finishing tool 10 to the driver 12. The annular chamber 44 is connected by means of passages 46 to a central axial chamber 48 in the body 32. This central axial chamber 48 is connected through the driver 12 to the pressurized fluid supply conduit 28. Hence, the pressurized fluid flows into the annular chamber 44 between the cylindrical body 32 and the sleeve 40 to serve as a means for expanding the sleeve 40 relative to the cylindrical body 32. It should be noted that the cylindrical body 32 is slid into the sleeve 40 and sweat soldered thereto near the nose end of the tool.

The outer surface of the expandable member 40 is adapted to serve as the cutting surface for the finishing tool 10. This cutting surface may be of any suitable type for sizing and finishing the inside diameter of a hole. In this particular embodiment the tools cutting action is derived from a composite of diamonds (or other abrasives, such as carbide aluminum or oxide) and nickel in an electrochemical plating 50 on the outer patterned surface of the expandable sleeve 40. This plating surface 50' is arranged to include a patterned plurality of diamond shaped raised cutting portions 52 separated by relief areas 54. The purpose of the alternating raised and relief portions is twofold. First, the relief areas 54' provide a flow path for coolant and lubricant between the cutting portions 52, and secondly, the pattern is used to minimize the area in contact with the material of the body being finished, thereby reducing the amount of frictional heat produced by the finishing operation. A plurality of very small holes 56 are cut through the plating surface 50 and the expandable sleeve 40 to connect the cutting surface with the annular chamber 44. This thereby allows the pressurized fluid within the chamber 44 to flow out onto the surface of the cutting tool to serve as both a lubricant and coolant for the cutting surface of the tool. The holes 56 are small enough so that the flow through them is slight, thereby allowing the pressure of the fluid in chamber 44 to build up so that it can be used to expand the sleeve 40. Hence, in operation, the pressurized fluid in the chamber 44 serves both as a lubricant and cooling means for the outer cutting surface of the tool and as a pressure producing means to expand the sleeve 40 relative to the cylindrical body 32.

It has been found that this finishing tool has exceptional capabilities for finishing a hole round to within .000003 to .000005 inch. It has also been found that a tool of .300 inch diameter has an expansion range of .000100 inch. This amount of exapnsion for a tool of this type is proportional to the tool diameter. Hence, this tool embodying the subject invention permits hole finishing in both hard and soft metals to rnicroinch tolerances at a high production rate by comparison to currently available such tools. When the tool changes its cutting size due to wear, this size is maintained by increasing the pressure of the fluid in chamber 4-4, thereby expanding the sleeve 40 to return the cutting surface 50 to its desired s1ze.

Hence, the subject invention presents a finishing tool for sizing to extremely accurate dimension a previously made hole. This finishing tool as it has been explained overcomes the disadvantages associated with currently used reaming or sizing tools.

Although but one embodiment of the subject invention has been shown and described in detail, it should be obvious to those skilled in the art to which the invention pertains that many modifications and changes may be made thereto without departing from the scope of the invention.

I claim:

1. An expandable finishing tool for finish machining cylindrical holes in workpieces with high accuracy, adapted to be aligned with the workpiece by circumferential contact between the tool and the walls of the hole, to be simultaneously rotated and reciprocated by a driving device, and to be connected to a source of variably pressurized fluid: the tool comprising, in combination, a generally cylindrical elongate rigid core; an expandable thin hollow rigid elastic cylindrical sleeve extending over at least a substantial portion of said core, the sleeve and core being in contact through an annular zone at each end of the overlap between the sleeve and core and being spaced throughout the portion between the said annular zones to define an annular fluid chamber between the core and sleeve; the sleeve being formed with a multiplicity of axially and circumferentially distributed lands lying in a cylindrical surface of diameter corresponding to that of the finished hole size, the lands being separated by depressed areas, each land providing a machining surface; and a thin abrasive external facing on the sleeve covering at least the exterior of the said lands; the core defining a passage adapted to connect the source of fluid to the fluid chamber; the diameter of the abrasive coating being variable, for precision control of hole size and to compensate for wear of the abrasive coating, by elastic expansion of the sleeve effected by variation of the pressure of the said fluid within the said chamber; and the straightness of the sleeve being enhanced by the engagement of the sleeve and core at the said zones.

2. A tool as recited in claim 1 in which the lands are substantially of rhombic outline with diagonals extending substantially axially and circumferentially of the sleeve.

3. A tool as recited in claim 1 in which the said facing is a plating of nickel and diamonds.

4. A tool as recited in claim 1 in which the sleeve includes means for direct connection of the sleeve to the driving device and the core is connected to the sleeve to be driven by the sleeve.

5. A tool as recited in claim 4 with a slidable connection between the sleeve and core at the zone nearest the said connection means and a fixed connection at the other zone.

6. A tool as recited in claim 4 in which the core extends axially from the end of the sleeve remote from the said connection means and defines a tapering work entering nose.

References Cited UNITED STATES PATENTS 2,000,330 5/1935 High 51349 2,017,163 10/1935 Reed 5l373 2,605,594 8/1952 Macdonell 51--373 FOREIGN PATENTS 457,503 11/ 1936' Great Britain.

ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner U.S. Cl. X.R. 5l206, 356, 373 

